The cxpm program can be used
to check the format of any XPM (version 1, 2, or 3) file. On error, unlike
sxpm, cxpm prints out an error message indicating where the parser choked.
This should help finding out what's wrong with an XPM file but do not expect
too much from it though. This is not even close from being some kind of
lint program for XPM. First, it stops at the first error it encounters -
so several fix and retry cycles may be necessary to get your file to parse
successfully. Second, cxpm only cares about the format. If, for instance,
your pixmap uses too many colors for your system you still may experience
difficulties displaying it. Be warned.